title: Chronic exposure of river sediments to environmentally relevant levels of tetracycline affects bacterial communities but not denitrification rates.
abstract: The effects of tetracycline (TC) at chronic sub-inhibitory exposure concentrations on benthic denitrification rates and bacterial communities were explored. River sediments were continuously exposed to different TC concentrations (0.5, 20 and 10,000 μg L(-1)) for 2 weeks in flow-through reactors allowing denitrification and bacterial growth conditions. Bacterial communities were fingerprinted by Denaturing Gradient Gel Electrophoresis of 16S rRNA gene amplification products. Cultivable denitrifiers enriched from the sediment were tested for TC resistance (2-128 mg L(-1)). Denitrification rates were unaffected by exposure to TC, regardless of concentration. In contrast, the bacterial community composition changed significantly from sub-inhibitory (ng-μg L(-1)) to therapeutic (mg L(-1)) exposure concentrations. Furthermore the cultivable denitrifiers showed a high TC sensitivity (<4 mg L(-1)). Maintenance of efficient benthic denitrification rates, even at the highest level of TC exposure most likely originated from an adaptation of the autochthonous bacterial community where dominant species become those that acquire, or already have resistance to antibiotics.
authors.affiliation: Université Pierre et Marie Curie, UMR 7619 Sisyphe, Box 123, 75005, Paris Cedex 05, France, celine.amsaleg@upmc.fr.
authors.forename: Céline
authors.initials: C
authors.lastname: Roose-Amsaleg
authors.forename: Chen
authors.initials: C
authors.lastname: Yan
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Hoang
authors.forename: Anniet M
authors.initials: AM
authors.lastname: Laverman
mesh_terms: D000900:Anti-Bacterial Agents / Q000633:toxicity*; D001419:Bacteria / Q000187:drug effects*; D058645:Denaturing Gradient Gel Electrophoresis; D058440:Denitrification / Q000187:drug effects*; D005602:France; D019015:Geologic Sediments / Q000032:analysis / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D045483:Rivers / Q000382:microbiology; D013752:Tetracycline / Q000633:toxicity*; D013753:Tetracycline Resistance; D014874:Water Pollutants, Chemical / Q000627:therapeutic use*
chemical_list: D000900:Anti-Bacterial Agents; D012336:RNA, Ribosomal, 16S; D014874:Water Pollutants, Chemical; D013752:Tetracycline